Article Categories
- All Categories
-
Data Structure
-
Networking
-
RDBMS
-
Operating System
-
Java
-
MS Excel
-
iOS
-
HTML
-
CSS
-
Android
-
Python
-
C Programming
-
C++
-
C#
-
MongoDB
-
MySQL
-
Javascript
-
PHP
-
Economics & Finance
Articles on Trending Technologies
Technical articles with clear explanations and examples
How to Fill the Entries in Parsing Table?
A parser is the second phase of compilation. The parser takes as its input tokens generated from the previous phase, i.e., the Lexical Analyzer phase, and groups them in such a way that their syntax can be recognized.For example, Consider I0I0 − E′ → ∙ E E → ∙ E + T E → ∙ T T → ∙ T ∗ F T → ∙ F F → ∙ (E) F → ∙ idFilling of Shifting EntriesApplying Rule (2a) of the algorithm of construction of SLR Parsing Table on a set of a ...
Read MoreR Programming to find the column name for row maximum in a data.table object.
If we have a data.table object and we want to find the column name for row maximum then we can use max.col function.For Example, if we have a data.table object called DT then we can find the column name for row maximum by using the below command −DT[,names(.SD)[max.col(.SD,ties.method="first")]]Example 1Following snippet creates a sample data frame −x1
Read MoreConstruct SLR (1) parsing table for the grammarn1. E → E + Tn2. E → Tn3. T → T * Fn4. T → Fn5.F → (E)n6.F → id
SolutionSteps to produce SLR Parsing TableGenerate Canonical set of LR (0) itemsCompute FOLLOW as required by Rule (2b) of Parsing Table Algorithm.Computation of FOLLOWBy Rule (1) of FOLLOWFOLLOW(E) = {$} (1)E → E + TApplying Rule (2) FOLLOWi.e., comparing E → E + T with A → α B βE →ΕE+ TA →ΑBΒ∴ A = E, α = ε, B = E, β = +T∵ Since FIRST(β) = FIRST(+T) = {+}which does not contain ε.∴ ...
Read MoreWhat is SLR (1) Parser?
SLR represents "Simple LR Parser". It is very simple and economical to execute. But it fails to make a parsing table for some class of grammars, i.e., why CLR and LALR are used which implements mainly all class or type of grammars. It constructs parsing tables which helps to perform parsing of input strings.SLR(1) − A grammar having an SLR parsing table is said to be SLR (1).Working of SLR ParserSLR Parsing can be done if context-free Grammar will be given. In LR (0), 0 means there is no Look Ahead symbol.The Canonical collection of LR (0) itemsThe LR (0) ...
Read MoreRemove rows from a data frame that exists in another data frame in R.
To remove rows from a data frame that exists in another data frame, we can use subsetting with single square brackets. This removal will help us to find the unique rows in the data frame based on the column of another data frame.Check out the below Examples to understand how it can be done.Example 1Following snippet creates a sample data frame −x
Read MoreFind the canonical collection of sets of LR (0) items for Grammar -nE → E + TnE → TnT → T * FnT → FnF → (E)nF → id
SolutionStep1− Construct the Augmented Grammar and number the productions(0) E′ → E(1) E → E + T(2) E → T(3) T → T * F(4) T → F(5) F → (E)(6) F → idStep2− Apply closure to the set of items & find gotoSquare Boxes represent the new states or items, and Circle represents the repeating items.So, all rules of I0have been completed by applying goto on I0. Now, in the same manner apply goto on I1, I2 and then goes on.Drawing DFAEach set of the item can be taken as a state of DFA, i.e., I0, I1 … … ...
Read MoreAdd values in sequence to the previous value with a constant.
To add values in sequence to the previous value with a constant, we can find the cumulative sum of values and add the constant to the Output.For Example, if we have a vector called X and we want to add values in X in sequence to the previous value with a constant say 10 then we can use the command given below −10+cumsum(X)Example 1Following snippet creates a sample data frame −x1
Read MoreCreate cross tabulation for three categorical columns in an R data frame.
To create cross tabulation for three categorical columns, we can use xtabs function. The xtabs function will create contingency table for each category in two columns and each contingency table will be created for the category in the third column.Check out the below Examples to understand how it can be done.Example 1Following snippet creates a sample data frame −df1
Read MoreWhat is Algorithm of Predictive Parsing and compute FIRST and FOLLOW for the following GrammarnS → L = RnS → RnL →* RnL → idnR → L
SolutionComputation of FIRSTS → L = R∵ L does not derive ε. By rule (4b)of FIRST∴ FIRST(S) = {FIRST(L)} (1)S → R∵ R does not derive ε. By rule (4b)of FIRST∴ FIRST(S) = {FIRST(R)} (2)L →* RApplying Rule (3) of FIRSTFIRST(L) = {*} ...
Read MoreR Programing to change the name of column variable and row variable in xtab table.
To change the name of column variable and row variable in xtab table, we can use setNames function.For Example, if we have a xtab table called XTAB and we want to change the column variable name C and row variable name R then we can use the below command −dimnames(XTAB)
Read More